Amazon describes OpenSearch as an example of "vertical search." At the conference, Bezos demonstrated searching for "Vioxx" in a conventional search engine. Most of the results in a linear hit list will present the most popular Web pages containing that term. But if you use Amazon's A9 as your search engine, you can select PubMed as one of your trusted "columns." Then search A9 for Vioxx and you'll see scientific and clinical results from PubMed in addition to the traditional Web results.

A9 serves as a clearinghouse for OpenSearch contributors. Initial OpenSearch adopters include The New York Times Company, Flickr (a photo-sharing community recently acquired by Yahoo!), The British Library, and a localized Yellow Pages service provided by A9. To see a list of initial contributors, visit http://opensearch.a9.com/-/search/moreColumns.jsp.

Searchers can take advantage of OpenSearch by visiting the A9 service at http://a9.com. Click on the link labeled "Add Columns to Your Search Results." (If you have not signed in as an Amazon customer, you are only allowed to add one OpenSearch column to your collection of sites.) Search for a topic of interest (e.g., "living will") and you'll see results that look pretty much like a typical Google hit list. Now, select your chosen columns by clicking on corresponding buttons on the right of the screen and A9 will squeeze the traditional hit list to the left and add the sources you've selected each in its own column.

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As you select each content provider, A9 sends a query to the corresponding content provider's search engine in real time. Subsequent A9 searches will search all the content providers you've selected and present results in the columnar display. If the content provider's search engine is unreachable or unresponsive, the corresponding column will show an error message.

OpenSearch makes it possible for any content provider to export the functionality of its local site search engine to other Web sites. Amazon argues that traditional search engines often cannot do a good job of indexing content at specialized Web sites and that local search engines may understand local content far better: "Different types of content require different types of search engines. And most of the time, the best search engines for a site are the ones written by those that know the content the best" (from the OpenSearch FAQ located at http://opensearch.a9.com/docs/faq.jsp).

As a content provider, you might ask how exporting your search to another site is different from having a visitor come to your site and provide a local search. Consider the PubMed example. Visitors to A9 may not know how rich and authoritative a source PubMed is, but, when they see it on the list of available A9 columns, they may decide to add it to their collection of trusted sources. Just as an RSS feed for Wired magazine or a popular blog extends the audience of that content, syndicating your search opens it up to potential new eyeballs. This, of course, means that A9's own list of trusted sources becomes precious real estate.

The RSS and search industry communities are abuzz over OpenSearch. Some see Amazon grabbing mindshare and eyeballs from Google, Yahoo!, and other rivals—ironic in the case of Google, A9's Web search engine. While commenting in pioneering RSS developer Dave Winer's blog, Elle Webb wrote:

The significance is that this takes search results and cuts out the UI [user interface]. Interesting for developers, bad for search vendors that want to make money displaying ads. By creating a simple API standard for search results, Amazon is not creating a super search engine, but making everyone a competitor for Google, AOL, and MSN.

Once you publish the RSS interface into your site search, presumably any site on the Web could offer its own search window into your site. It will be interesting to see which new vertical search portals arise.

To accomplish search syndication, OpenSearch extends RSS technology. RSS is an XML-based way to deliver news headlines and other information. RSS was born in the late 1990s and was adopted by Netscape in 1999. Major tech publishers such as Wired adopted RSS as a way to get their headlines embedded in Web pages of willing content providers. The recent explosion of interest in blogging brought a parallel explosion of RSS adoption, because most Weblog hosting platforms make it easy to provide RSS feeds. Amazon calls its use of RSS "a straightforward and backward-compatible extension of RSS 2.0."

RSS traditionally has been used to feed news or article headlines to a cooperating Web site, which uses an "aggregator" to interpret the XML content and turn it into HTML, formatted as the receiving site sees fit. OpenSearch allows a content provider such as NASA or The British Library to export search functionality to other sites instead of headlines.

One thing likely to confuse people seeking to learn more about OpenSearch is that "opensearch.com" is a domain registered in 1995 by an Internet hosting provider in Perth, Australia. The URL for the new Amazon service is http://opensearch.a9.com. The term OpenSearch was also used by the late P2P pioneer Gene Kan to describe a distributed search tool for which a patent remains pending.